This invention relates to speakers and more particularly it deals with a novel speaker including a diaphragm which is a sound producing cone section filled with foamed resin of substantially low density and having a thin sheet on the surface of the foamed resin.
Diaphragms filled with foamed resin have hitherto had improved sound producing conditions and better frequency characteristics of an output sound range than diaphragms of no foamed resin, and have been able to move as a rigid body in vibration throughout the cone as a unitary structure over an entire sound range from a low to a high sound range.
Some disadvantages are, however, associated with diaphragms having foamed resin filled therein. Since a mass of foamed resin is additionally applied to the diaphragm if it has the foamed resin, the diaphragms have reduced electroacoustic transducing efficiency because of the increased mass. Thus, in order to avoid a reduction in transducing efficiency, it has hitherto been necessary to use foamed resin of as low a density as is practical as long as the end of filling the diaphragm with the resin is not defeated, to thereby minimize an increase in the mass of the diaphragm. When this is the case, there has been the disadvantage that when the operator touches the diaphragm by hand, the foamed resin might be damaged or dented.